Southern Research Institute/US EPA
April 2008
THE ENVIRONMENTAL TECHNOLOGY VERIFICATION PROGRAM
Environmental and Sustainable Technology Evaluation (ESTE)
&EPA
U.S. Environmental Protection Agency SOUTHERN RESEARCH
INSTITUTE
ESTE Joint Verification Statement
TECHNOLOGY TYPE: Biomass Co-firing
APPLICATION: Industrial Boilers
TECHNOLOGY NAME: Renewafuels Palletized Wood Fuel
COMPANY: Renewafuels, LLC
ADDRESS' 13420 Courthouse Boulevard
Rosemount, MN 55068
The U.S. Environmental Protection Agency (EPA) has created the Environmental Technology
Verification (ETV) program to facilitate the deployment of innovative or improved environmental
technologies through performance verification and dissemination of information. The goal of the ETV
program is to further environmental protection by accelerating the acceptance and use of improved and
cost-effective technologies. ETV seeks to achieve this goal by providing high-quality, peer-reviewed data
on technology performance to those involved in the purchase, design, distribution, financing, permitting,
and use of environmental technologies. This verification was conducted under the Environmental and
Sustainable Technology Evaluation (ESTE) program, a component of ETV that was designed to address
agency priorities for technology verification.
The goal of the ESTE program is to further environmental protection by substantially accelerating the
acceptance and use of improved and innovative environmental technologies. The ESTE program was
developed in response to the belief that there are many viable environmental technologies that are not
being used for the lack of credible third-party performance data. With performance data developed under
this program, technology buyers, financiers, and permitters in the United States and abroad will be better
equipped to make informed decisions regarding environmental technology purchase and use.
This ESTE project involved evaluation of co-firing common woody biomass in industrial, commercial or
institutional coal-fired boilers. For this project ERG was the responsible contractor and Southern
Research Institute (Southern) performed the work under subcontract. Client offices within the EPA, those
with an explicit interest in this project and its results, include: Office of Air and Radiation (OAR),
Combined Heat and Power (CHP) Partnership, Office of Air Quality Planning and Standards (OAQPS),
Combustion Group, Office of Solid Waste (OSW), Municipal and Industrial Solid Waste Division, and
ORD's Sustainable Technology Division. Letters of support have been received from the U.S.
Department of Agriculture Forest Service and the Council of Industrial Boiler Owners.
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TECHNOLOGY DESCRIPTION
Wood Pellets from a Renewafuel, LLC facility in Michigan were used for this verification. The pellets
were a pressed oak product which is made from the waste of trailer bed manufacturing. No glue or
adhesives were used in the manufacture of the pellets. Proximate analyses of the pelletized wood used for
this testing is as follows:
Component % by Weight
Moisture 6.6
Ash 0.43
Volatile matter 75.5
Fixed carbon 17.3
The average heating value was 7,688 British thermal units per pound (Btu/lb).
Testing was conducted at the University of Iowa (UI) Main Power Plant's Boiler 10. The UI Main Power
Plant is a combined heat and power (CHP) facility which serves the main campus and the UI hospitals
and clinics. The plant continuously supplies steam service and cogenerated electric power. There are
four operational boilers at the facility, one stoker unit (Boiler 10), one circulating fluidized bed boiler
(Boiler 11), and two gas package boilers (Boilers 7 and 8). Boiler 10 was used during this co-firing
demonstration. Boiler 10 is a Riley Stoker Corporation unit rated at 170,000 Ib/h steam (206 MMBtu/h
heat input) at 750 degrees Fahrenheit (°F) and 600 pounds per square inch, gauge (psig). This unit
normally operates in pressure control (swing) mode on a multi-boiler header at a typical operating range
of 120,000 to 140,000 Ib/h steam. The unit can be base loaded up to its rated capacity or swing down to a
minimum load of 90,0001b/h. The facility includes a mechanical dust collector and electrostatic
precipitator (ESP) to control paniculate emissions. Bottom ash and fly ash generated by Boilers 10 and
11 are collected, blended, and shipped to a nearby limestone quarry where it is mixed with water,
solidified, and used to build roads or fill.
Forty-four tons (T) of Renewafuel's wood based pellets were delivered to the River Trading site and
mixed with stoker coal using a front end loader. The weight of the total mixture was 294 T, for a pellet
fraction by weight of approximately 15 %.
VERIFICATION DESCRIPTION
This project was designed to evaluate changes in boiler performance due to co-firing woody biomass with
coal. Boiler operational performance with regard to efficiency, emissions, and fly ash characteristics
were evaluated while combusting 100 percent coal and then reevaluated while co-firing biomass with
coal. The verification also addressed sustainability issues associated with biomass co-firing at this site.
The testing was limited to two operating points on Boiler 10:
• firing coal only at a typical nominal load
• firing a coahbiomass "co-firing" mixture of approximately 85:15 percent by weight
at the same operating load
Under each condition, testing was conducted in triplicate with each test run approximately three hours in
duration. In addition to the emissions evaluation, this verification addressed changes in fly ash
composition. Fly ash can serve as a portland cement production component, structural fill, road materials,
soil stabilization, and other beneficial uses. An important property that limits the use of fly ash is carbon
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content. Presence of metals in the ash, particularly mercury (Hg), can also limit fly ash use, such as in
cement manufacturing. Biomass co-firing could impact fly ash composition and properties, so this
verification included evaluation of changes in fly ash carbon burnout (loss on ignition), minerals, and
metals content.
During testing, the verification parameters listed below were evaluated. This list was developed based on
project objectives cited by the client organizations and input from the Biomass Co-firing Stakeholder
Group (BCSG).
Verification Parameters:
• Changes in emissions due to biomass co-firing including:
- Nitrogen oxides (NOX)
- Sulfur dioxide (SO2)
- Carbon monoxide (CO)
- Carbon dioxide (CO2)
- Total particulates (TPM) (including condensable particulates)
- Primary metals: arsenic (As), selenium (Se), zinc (Zn), and Hg
- Secondary metals: barium (Ba), beryllium (Be), cadmium (Cd), chromium (Cr), copper (Cu),
manganese (Mn), nickel (Ni), and silver (Ag)
- Hydrogen chloride (HC1) and hydrogen fluoride (HF)
• Boiler efficiency
• Changes in fly ash characteristics including:
- Carbon, hydrogen, and nitrogen (CHN), and SiO2, A12O3, and Fe2O3 content
- Primary metals: As, Se, Zn, and Hg
- Secondary metals: Ba, Be, Cd, Cr, Cu, Mn, Ni, and Ag
- fly ash fusion temperature
- Resource Conservation Recovery Act (RCRA) metals and Toxic Characteristic Leaching
Procedure (TCLP).
• Sustainability indicators including CO2 emissions associated with sourcing and transportation of
biomass and ash disposal under baseline (no biomass co-firing) and test case (with biomass co-
firing) conditions.
Rationale for the experimental design, determination of verification parameters, detailed testing
procedures, test log forms, and QA/QC procedures can be found in Test and Quality Assurance Plan titled
Test and Quality Assurance Plan - Environmental and Sustainable Technology Evaluation Biomass Co-
firing in Industrial Boilers.
Quality Assurance (QA) oversight of the verification testing was provided following specifications in the
ETV Quality Management Plan (QMP). Southern's QA Manager conducted an audit of data quality on a
representative portion of the data generated during this verification and a review of this report. Data
review and validation was conducted at three levels including the field team leader (for data generated by
subcontractors), the project manager, and the QA manager. Through these activities, the QA manager has
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concluded that the data meet the data quality objectives that are specified in the Test and Quality
Assurance Plan.
VERIFICATION OF PERFORMANCE
Boiler Efficiency
For the efficiency testing, mass feed of blended coal and wood was increased to attempt to repeat heat
input as closely as possible to the baseline coal only tests.
Table S-1. Boiler Efficiency
Test ID
Baseline 1
Baseline 2
Baseline 3
Baseline 4
Cofire 1
Cofire 2
Cofire 3
Baseline Average
Cofire Average
Absolute Difference
% Difference
Fuel
100% Coal
Blended Fuel
(85.1 coal:
14.9 wood)
Statistically Significant Change?
Heat Input
(MMBtu/hr)
264.6
264.2
264.8
267.6
275.7
271.9
272.5
265.3
273.4
8.1
3.0%
na
Heat Output
(MMBtu/hr)
224.4
223.9
223.7
228.8
229.7
230.0
230.3
225.2
230.0
4.8
2.1%
na
Efficiency
(%)
84.8
84.8
84.5
85.5
83.3
84.6
84.5
84.9 ±0.4
84.1 +0.7
-0.7
-0.9%
No
The average efficiencies during baseline (coal only) and co-firing tests were 84.9 ± 0.4 and 84.1 ± 0.7
percent respectively. This change is not statistically significant, so it is concluded that co-firing biomass
at the 15 percent blending rate did not impact boiler efficiency performance.
Emissions Performance
Table S-2. Gaseous Pollutant Emissions (Ib/MMBtu)
Test ID
Fuel
SO,
CO,
NOX
CO
Baseline 1
Baseline 2
Baseline 3
Baseline 4
Cofire 1
Cofire 2
Cofire 3
Baseline Averages
Cofire Averages
% Difference
Statistically Signific
100% Coal
Blended Fuel
(85.1 coal:
14.9 wood)
ant Change?
2.49
2.28
2.48
2.63
2.12
2.11
2.26
2.47 ±0.14
2.16 ±0.08
-12.4%
Yes
207
206
206
202
207
207
207
205 ±2
207 ±0.3
0.82%
No
0.473
0.442
0.438
0.486
0.487
0.525
0.506
0.460 ±0.02
0.506 ±0.018
10.2%
Yes
0.081
0.083
0.085
0.102
0.089
0.081
0.081
0.088 ±0.010
0.083 ±0.05
-5.02%
No
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April 2008
SO2 emissions were about 13 percent lower while combusting the blended fuel, which correlates well
with the approximately 15 percent biomass to coal ratio. The reduction in SO2 indicates that co-firing
woody biomass may be a viable option for reducing SO2 emissions without adding emission control
technologies. NOX emissions had a statistically significant increase when co-firing. Increases are
presumably due to the higher temperatures within the boiler that were experienced while firing the dryer,
lighter blended fuel. Changes in CO and CO2 emissions were not statistically significant.
Table S-3. Paniculate Emissions (Ib/MMBtu)
Test ID
Baseline 1
Baseline 2
Baseline 3
Baseline 3
Cofire 1
Cofire 2
Cofire 3
Baseline Averages
Cofire Averages
Absolute Difference
% Difference
Fuel
1 00 % Coal
Blended Fuel
(85.1 coal: 14.9
wood)
Statistically Significant Change?
Total Particulate
0.090
0.039
0.054
Filterable PM
0.038
0.023
0.031
Condensable
PM
0.051
0.016
0.022
Not Tested
0.046
0.044
0.041
0.061 ±0.03
0.044 ±0.003
-1.71E-02
-28.1%
No
0.026
0.023
0.023
0.031 ±0.008
0.024 ±0.001 8
-7.03E-03
-22.8%
No
0.021
0.020
0.018
0.030 ±0.02
0.020 ±0.001 2
-1.01E-02
-33.9%
No
Although not statistically significant, particulate emission fractions were generally lower while co-firing
the blended fuel. This is likely caused by the lower ash content of the blended fuels. It could also be the
result of better combustion or better ESP performance due to changes in firebox temperatures or flyash
characteristics.
Metals emissions were relatively low during all test periods. The only statistically significant change in
metals emissions was a decrease in selenium. Emissions of HC1 and HE were considerably lower during
co-firing decreasing by approximately 9 and 29 percent, respectively.
Fly Ash Characteristics
Changes in ash characteristics were generally small, which is favorable for most operating systems (ash
handling systems would not be expected to be impacted by co-firing at this rate). Carbon content and ash
loss on ignition were both reduced significantly during biomass co-firing, although neither ash met the
Class F requirements for use in concrete. Quantitative flyash results are voluminous and not presented
here, but can be viewed in the main body of the report in Tables 3-7 through 3-9.
Biomass co-firing during this verification did not impact the quality of the ash with regard to fly ash
TCLP metals (40 CFR 261.24) and Class F Requirements (C 618-05). Metals content of the ash was well
below the TCLP criteria during all test periods and changes were not significant. The ash generated
during co-firing did have a significantly higher SO3 content, but was still well below the Class F
requirement.
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Sustainability Issues
• The wood pellets used for testing at the University of Iowa were produced from waste wood
waste at a rate of 4.5 tons per hour. The equipment used to produce the pellets is rated at 250
horsepower and was operated at 80 percent of capacity. Based on electrical consumption of
0.746 kWh/hp multiplied by 200 hp, the energy use per hour to produce the pellets was 149.14
kWh or 33.14 kWh/ton. Based on an Energy Information Administration emission factor for
Michigan (location of the production facility) of 1.58 Ibs CO2/kWh, CO2 emissions per ton of
pellets produced is 52.36 Ibs.
• Wood-based pellets were transported from Battle Creek Michigan to Muscatine, Iowa (where the
University of Iowa's coal supplier is located). 43 tons of wood-based pellets were shipped with
two trucks using 350 Cummins motors. The trucks averaged 6.5 miles per gallon. The distance
from Battle Creek to Muscatine is 345 miles. Therefore:
345 miles * 2 trucks = 690 miles, divided by 6.5 mpg = 106.15 gallons, divided by 43
tons fuel = 2.47 gallons/ton.
Renewafuel has a 28-acre site for possible future operations in Anamosa, Iowa. The distance
from Anamosa to Muscatine is 65 miles. Here, Renewafuel can load as much as 25 tons of fuel
per truck. Assuming use of the same truck with 6.5 miles per gallon the fuel used per ton of fuel
transported from Anamosa to Muscatine, fuel usage from Anamosa is then:
65 miles, divided by 6.5 mpg = 10 gallons, divided by 25 tons per truck = 0.4 gallons/ton
• Based on an Energy Information Administration emission factor of 19.564 Ibs CO2/gallon, CO2
emissions per ton of pellets transported to the facility are:
48.3 Ibs/ton for Battle Creek (2.47 gal fuel /ton pellets * 19.564 Ibs CO2/gal).
7.82 Ibs/ton for Anamosa (0.4 gal/ton * 19.564 Ibs CO2/gal).
• Based on data generated during this testing, the CO2 emission rates while firing straight coal and
blended fuel (at a blending rate of approximately 15 percent wood by mass) were 205 and 207
Ib/MMBtu, respectively. However, combustion of Renewafuel wood pellets, which are
comprised of biogenic carbon—meaning it is part of the natural carbon balance and will not add
to atmospheric concentrations of CO2—emits no creditable CO2 emissions under international
greenhouse gas accounting methods developed by the IPCC and adopted by the CFPA [6]. The
slight increase in CO2 emissions is likely also impacted by the increased mass fuel feed rates
during co-firing. By analyzing the heat content of the coal and the wood, the total boiler heat
input for the test periods, and boiler efficiency, it was determined that approximately 10 percent
of the heat generated during co-firing test periods is attributable to the Renewafuel pellets fuel. It
is therefore estimated that the CO2 emissions offset during this testing is approximately 10
percent, or 20.7 Ib/MMBtu at this co-firing blend.
• UI Boiler 10 typically operates in the 160 to 190 MMBtu/hr heat generating rate. Assuming an
availability and utilization rate of 80 percent for Boiler 10, this would equate to estimated annual
CO2 emission reductions of approximately 11,000 to 13,000 tons per year. CO2 offsets from use
of wood pellets could be even greater had the analysis included emissions associated with coal
mining and transportation.
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• Regarding use and or disposal of fly ash, biomass co-firing did not impact either sustainability
issue since the quality of the ash with regard to fly ash TCLP metals and Class F Requirements
was unchanged.
Details on the verification test design, measurement test procedures, and Quality Assurance/Quality Control
(QA/QC) procedures can be found in the Test Plan titled Test and Quality Assurance Plan - Environmental
and Sustainable Technology Evaluation Biomass Co-firing in Industrial Boilers. (Southern 2006). Detailed
results of the verification are presented in the Final Report titled Environmental and Sustainable Technology
Evaluation Biomass Co-firing in Industrial Boilers - University of Iowa (Southern 2007). Both can be
downloaded from the Southern's web-site (www.sri-rtp.com) or the ETV Program web-site
(ww w. epa. eov/etv).
Signed by: Sally Gutierrez - April 28, 2008 TimHansen-April 3, 2008
Sally Gutierrez Tim Hansen
Director Program Director
National Risk Management Research Laboratory Southern Research Institute
Office of Research and Development
Notice: This verification was based on an evaluation of technology performance under specific, predetermined
criteria and the appropriate quality assurance procedures. The EPA and Southern Research Institute make no
expressed or implied warranties as to the performance of the technology and do not certify that a technology will
always operate at the levels verified. The end user is solely responsible for complying with any and all applicable
Federal, State, and Local requirements. Mention of commercial product names does not imply endorsement or
recommendation.
EPA REVIEW NOTICE
This report has been peer and administratively reviewed by the U.S. Environmental Protection Agency, and
approved for publication. Mention of trade names or commercial products does not constitute endorsement or
recommendation for use.
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